SW6231201_Response To Comments_20240305

MCADAMS RESPONSE TO COMMENTS > DKE22043
March 5, 2024
Jim Farkas, State Stormwater Engineer
North Carolina Department of Environmental Quality
Division of Energy, Mineral and Land Resources
512 North Salisbury Street, Office 640M
Raleigh, North Carolina 27604
RE: Erwin-Fayetteville 115kV Completion
NCDEQ Permit#:SW6231201
Response to Old Bluff Church Road Comments (02-27-2024)
DKE22043
The following are the response comments for the above-mentioned project. Our response comments are in bold.
NCDEQ—POST CONSTRUCTION STORMWATER PERMITTING GROUP
Jim Farkas 919. 707. 3646
1. Please ensure that the entire on-site surface water area is accounted for in the Application and Supplement-EZ
Form (per 15A NCAC 02H .1003(1)(c)(i)). Per the other submittal items,the project area is shown as 30.92 ac and
per the plans in the stormwater report,the on-site surface water area is 1.01 ac (0.46 ac for the pond and 0.55
ac for the stream). Subtracting the surface water area from the property area would result in a project area of
29.91 ac. Please make the following corrections:
a. Application:
i. Section IV, 6—Revise the surface water area (1.01 ac).
ii. Section IV, 7—Recalculate this value (29.91 ac).
iii. Section IV, 8—Recalculate this value (19.1%).
McAdams Response:These values have been updated as requested.
b. Supplement-EZ Form, Cover Page:
i. Line 2—Revise the project area (29.91 ac).
ii. Line 4—Revise the surface water area (1.01 ac).
McAdams Response:These values have been updated as requested.
2. For a low-density project,the "drainage area" of the project is equal to the project area (not necessarily the area
draining to any on-site vegetated conveyances, see note in Section IV, 9 of the Application). Please make the
following corrections:
a. Application, Section IV, 10:
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MCADAMS RESPONSE TO COMMENTS > DKE22043
i. Total Drainage Area—Revise this value (equal to the sum of the on-site and off-site "drainage area"
values, in square feet).
ii. On-site Drainage Area—Revise this value (equal to the project area, 29.91 ac, in square feet).
iii. Off-site Drainage Area— Revise this value (low-density projects typically do not have an off-site
component as the low-density drainage area is equal to the project area).
iv. Percent Impervious Area—Recalculate this value (Total BUA/Total Drainage Area).
v. Off-site BUA—Revise this value (low-density projects typically do not have an off-site component as
the low-density drainage area is equal to the project area).
vi. Total BUA—Revise this value.
McAdams Response:These values have been updated as requested.
b. Supplement-EZ Form, Drainage Areas Page:
i. Line 5—Revise this value (equal to the sum of Lines 6 & 7, in square feet).
ii. Line 6—Revise this value (equal to the project area, 29.91 ac, in square feet).
iii. Line 7—Revise this value (low-density projects typically do not have an off-site component as the low-
density drainage area is equal to the project area).
iv. Line 18—Recalculate this value (Line 8/ Line 5).
v. Line 19—NOTE:This item is not required for low-density projects.
vi. LD 1 Column—Please complete this column. For this project, the values in this column will be equal to
the entire site column.
McAdams Response:These values have been updated as requested.
3. Please include the drainage area delineation to the vegetated conveyances in the main set of plans(required per
15A NCAC 02H .1042(2)(g)(iv) and Section VI,8o of the Application). It is noted that the drainage area map is
included in the calculations (which was used for review), however this needs to be provided in the main set of
plans. Please revise as needed.
McAdams Response:The drainage area delineation maps have been added to the plan set.
4. Please clarify the design information for the swale provided in the calculations.The Hydraflow calculation shows
a 10-year peak discharge rate of 39.9 cfs (based on C=0.6, i =7.93 in/hr, and A=8.39 ac) whereas the design
spreadsheet shows a 10-year peak discharge rate of 27.63 cfs (based on C=0.4, i = 7.93 in/hr, and A=8.71 ac).
Please revise the submittal materials as needed.
McAdams Response:The Hydraflow calculation has been updated to match the calculation in the design
spreadsheet.
5. Please correct the following issues with the Supplement-EZ Form, Low-Density Page:
a. Line 5—This value (4.91 fps) does not correspond to the largest swale velocity as shown in the swale table
(4.12 fps NOTE: See later comment with regard to swale velocities).
McAdams Response:These values have been updated as requested.
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MCADAMS RESPONSE TO COMMENTS > DKE22043
b. Please ensure that the swale design information shown in the swale table is indicative of the final proposed
site conditions. NOTE: Due to the temporary nature of this project,you may wish to list the two different
"Vallowable" & "Vactual"values (one with the temporary matting and one with the established vegetated
cover) in the swale table and include a note in the additional information section that the two entries shown
in the table refer to the same swale,just with different linings (we require that the swale design be shown
for final proposed site conditions, but most likely,this project will remain in the temporary site configuration
before being returned to the predevelopment conditions so also having the temporary swale design info in
the design table would be beneficial).
McAdams Response:These values have been updated as requested.
Consideration of this response is greatly appreciated. If you should have any questions or require additional
information, please do not hesitate to contact me at 919. 413. 8322.
Sincerely,
MCADAMS
Nick Parks
Senior Project Manager
N P/kt
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